June 20, 2012 -- For some people with Parkinson's disease, deep brain stimulation can have immediate and dramatic effects on
tremors, rigidity, balance, and other motor symptoms.

Now new research shows that these benefits may last at least three years. The findings appear online in Neurology.

Deep brain stimulation uses a battery-operated device to deliver electrical impulses -- similar to a pacemaker for the heart -- to areas of the brain that control movement. The impulses are thought to block abnormal signals that cause many of the movement problems (motor symptoms) of Parkinson's. This procedure is typically reserved for individuals who no longer respond to their Parkinson's medications or who experience unacceptable side effects from them.

According to the new findings, this treatment helped with motor symptoms such as tremor, but individuals did show gradual declines over time in their quality of life, ability to perform tasks of daily living, and thinking skills.

After the 'Wow Effect'

"This study looked past the immediate 'wow effect,'" says Michele Tagliati, MD. He wrote an editorial accompanying the new study.

"Now we want to know what we can expect over the next 10 years, and this starts to make it clearer," says Tagliati, the director of the Movement Disorders Program at Cedars-Sinai Medical Center in Los Angeles.

"The effect on motor function is sustained," says researcher Frances M. Weaver, PhD. She is the director of the Center for Management of Complex Chronic Care at Edward Hines Jr. VA Hospital in Hines, Ill. But "deep brain stimulation does not have an impact on the other symptoms of the disease, so there will be progression."

Weaver's study included 89 people whose device was implanted in a part of the brain called the globus pallidus interna (GP) and 70 who were stimulated in a part of the brain known as the subthalamic nucleus (STN).

While there were early improvements in quality of life and the abilities to perform activities of daily living, these gradually diminished, and there was a decline in mental abilities. This likely reflects the progression of the disease and the emergence of symptoms that are resistant to treatment, Weaver says.

The research still helps doctors in more ways than one, though. "People got a fairly even motor benefit from both implantation sites," says Stuart Isaacson, MD. He is the director of the Parkinson's Disease and Movement Disorders Center of Boca Raton, Fla., and an associate professor of neurology at Florida International University's Herbert Wertheim College of Medicine in Miami.

"This is hopeful because it allows different places for us to implant the device," he says. "We would expect the procedure to have a good benefit over years and years, but we just didn't have great evidence until now."

Isaacson reiterates that deep brain stimulation is not a cure for Parkinson's disease. "We are still looking for a cure, and this is a way of trying to manage the symptoms for a longer period of time while we await the cure."

Weaver agrees: "Deep brain stimulation is not a cure for Parkinson's disease, but it is a treatment option for many people who are no longer benefiting from their medication," she says.

Is Deep Brain Stimulation Right for You?

So when is the right time to talk to a doctor about deep brain stimulation? "When the medicine isn't working the way it used to, and you are having unpredictable motor function problems, it may be a good time to consider this surgery," Weaver says.

Not everyone with Parkinson's disease will be a candidate. People who have severe mental disability or other medical problems may not be eligible.

Location, Location, Location

Tagliati also says the findings help guide doctors on where in the brain to implant the device.

"Until this study, the decision of location was based on the experience, expertise, and mood of the surgeon or neurologist," he says. For a long time, the belief was that STN was a superior target.

But not according to the findings, Tagliati says. Those people whose device is implanted in the GP region of their brain may maintain thinking and mental faculties longer. "It was as if the disease did not progress as much as in [the] other group," he says.

This target may work better with medication than the other one.

Anyone considering this surgery should ask about the different targets and which makes more sense for them, he says.